Sharing Problem (XP Professional)

Does anyone know if there are problems with Permissions 'sticking' in XP? I have a friend who has 2 PCs connected together in an office environment. He has his secretary set up as a user with Full Permissions, however, whenever he saves a document or opens then resaves a document, his secretary cannot open it. If he resets the security settings by going to sharing and security for the shared folder, then security, then advanced settings, then hitting the replace permission entries, it resets the folder and his secretary can open the files. However, when he creates a new document or changes and saves an existing document, the same problem occurs, and he has to go through the whole procedure of resetting permissions.